Applied Geochemistry (v.25, #7)

The Swanscombe area of Kent, SE England represents a typical example of a heavily quarried Chalk area currently undergoing re-development. Because the Chalk is also an important aquifer, a good understanding of groundwater movement is required if environmental impacts are to be minimised and the water resource maximised. In particular, the nature of the relationship between the River Darent and groundwater in the Swanscombe Chalk Block requires better characterisation. Here, ‘environmental tracers’ in the form of ambient concentrations of stable isotopes, chlorofluorocarbons (CFCs), sulphur hexafluoride (SF6) and tritium (3H) are used to investigate this and other aspects of groundwater movement in the vicinity of the quarries. Stable isotopic contrasts indicate little evidence for widespread river infiltration to the regional Chalk aquifer, although stable isotope and 3H data suggest that 20–35% of the abstraction by river-valley public water supply boreholes may be derived from the river. The CFCs, while present at above-modern concentrations in almost all groundwaters, can be used as tracers, indicating basically S–N flowpaths in the area south of the quarries, though sub-karstic conduits associated with areas of Palaeogene cover add a level of uncertainty at the local scale. Simple piston flow residence times based on SF6 range from 1 to 17 a, but the data are probably better interpreted in terms of mixing between varying amounts of modern recharge derived from the south and deeper stored groundwater. The information gained from environmental tracers can therefore contribute to effective resource management.

This study presents the first organic geochemical and petrographical investigation of the Callovian deposits of the eastern part of the Central European Basin. It is shown that in both the terrigenous Papilė Formation (Lower Callovian) and shallow- to deeper-marine facies of the Papartinė and Skinija formations (Middle and Upper Callovian, respectively), terrestrial organic matter predominates. This is reflected by the carbon preference index values higher than 1.2 for all samples and in some cases higher than 2, as well as the occurrence of characteristic higher plant biomarkers like cadalene, dehydroabietane, simonellite and retene. Moreover, in the case of the Papilė Formation, sugiol – a natural product terpenoid produced by distinct conifer families, has been detected in clay sediments. The occurrence of such a biomolecule in the Middle Jurassic clays is reported for the first time. Its occurrence is probably connected with the presence of small wood debris in the clay sediments. In samples of the Papilė Formation, charcoal fragments co-occurring with unsubstituted polycyclic aromatic hydrocarbons were detected, indicating that wildfires took place during the Early Callovian of Lithuania and/or neighbouring areas. In the Middle and Upper marine Callovian sediments of Lithuania there is no evidence of anoxic conditions occurring in the water column. However, periodic anoxic or strongly dysoxic episodes may have occurred, most probably below the photic zone, during the deepest phase of the Late Callovian transgression, as is evidenced from pyrite framboid diameter distribution and general impoverishment of benthic fauna. Huminite reflectance (R r) values for the investigated area are in the range of 0.21–0.31%, suggesting the occurrence of immature organic matter. Such values indicate that these investigated deposits were close to the surface during their whole diagenetic history, and the thickness of younger cover did not exceed ca. 500 m. This is also supported by a biomarker analysis in which less thermally stable ββ-hopanes and hopenes significantly dominated.

Is there a possibility to correct fossil n-alkane data for postsedimentary alteration effects? by Björn Buggle; Guido L.B. Wiesenberg; Bruno Glaser (947-957).
The long chain n-alkane composition of plant material can significantly differ between plant groups e.g. trees and grasses. Due to their relative recalcitrance, they have been employed in paleoecological research as molecular proxies for different types of vegetation. Most of those paleoenvironmental studies rely on the assumption that characteristic molecular fingerprints of plant material are preserved in the fossil organic material without significant alteration. However, there exists evidence that n-alkane distributions may change in the course of plant litter degradation. Here, the authors propose and discuss a conceptual approach to the correction of n-alkane patterns in paleosols and terrestrial sediments for postsedimentary alteration effects. This might have potential to improve paleoenvironmental reconstructions derived from these molecular fossils. In soil depth profiles typically a correlation between the OEP (odd over even predominance) and paleoecological valuable long-chain n-alkane ratios (LARs) can be found. Similar relationships have been also obtained from n-alkane records in paleosols. With the OEP serving as a proxy of microbial reworking, the correction procedure applies OEP vs. LAR regression functions to correct fossil LARs for degradation effects. The regression functions have been derived from modern soils. The application of the procedure and its significance for paleoecological interpretations is demonstrated on a case study of a loess-paleosol sequence (∼400–700 ka) in Romania. It is shown that changes in the C27/C31 n-alkane ratio at this site are closely related to degradation effects rather than to changes in the paleovegetation (e.g. tree vs. grass abundance). However, it was found that the C29/C31 ratio is a more suitable paleoenvironmental proxy at the Mircea Voda site. The results indicate that there is a future potential to correct fossil n-alkane ratios via the OEP/LAR relationship, however at the moment a general straight forward application of this approach might be critical due to lack of extended and diverse n-alkane records from modern soils. The need of more systematic n-alkane studies on soil profiles is highlighted to improve knowledge concerning dynamics and actual mechanisms of postsedimentary LAR and OEP changes.

The aim of the study was to evaluate passive treatment system alternatives to mitigate acid mine drainage (AMD) characterized by low SO 4 2 - and metal concentrations associated with adit drainage at the Williams Brothers Mine located in the Sierra National Forest, California. Surface water from the site drains into the San Joaquin River Basin and a goal of this study was to mitigate AMD to meet water quality objectives for the San Joaquin River Basin. Effluent sampling from the opening of the lowermost adit identified (AMD) characterized by a pH of 3.90, average SO 4 2 - concentration of 101 mg/L and relatively low average metal concentrations of 4.60, 0.074, 0.047 and 0.133 mg/L for Fe, Cu, Ni and Zn, respectively. The bench-scale study involved the testing of three passive treatment systems: (1) a peat biofilter followed by an anoxic limestone drain (ALD); (2) a SO 4 2 - -reducing bacteria (SRB) bioreactor followed by an ALD; and (3) a single SRB bioreactor. Synthetic AMD was produced to represent the AMD characteristics observed at the site. The peat–ALD system efficiently increased the pH of the effluent to an average of 6.95. Metals were reduced to average concentrations of 0.06, 0.008, 0.013 and 0.057 mg/L, respectively, for Fe, Cu, Ni and Zn. The SRB–ALD system increased the effluent pH to an average of 6.47, decreased SO 4 2 - concentrations to an average of 11.6 mg/L and decreased the concentrations of Fe, Cu, Ni and Zn to averages of 1.04, 0.004, 0.016 and 0.025 mg/L, respectively. The SRB system efficiently increased the pH to an average of 6.56 and decreased SO 4 2 - concentrations to an average of 18.8 mg/L. Metal concentrations for Fe, Cu, Ni and Zn were reduced to 0.63, 0.006, 0.010 and 0.027 mg/L, respectively. The peat–ALD and SRB systems were capable of increasing the pH of the AMD to 6.5 to meet water quality objectives. The peat–ALD system was capable of removing Fe and Cu to below water quality objectives, however, removal of other metals was insufficient. The SRB containing systems were incapable of removing Fe to water quality objectives, while sufficient removal of Cu, Ni and Zn was attained. From these results, the most effective treatment system would incorporate a peat biofilter, for Fe and Cu removal and a SRB bioreactor for Cu, Ni and Zn removal. The results of this study demonstrate that passive treatment mitigation of AMD can best be accomplished via the use of a combined treatment system that incorporates a peat biofilter, SRB bioreactor and anoxic limestone drain, thereby accomplishing targeted removal of constituents in individual system components.

Chalcopyrite dissolution rate laws by Bryn E. Kimball; J. Donald Rimstidt; Susan L. Brantley (972-983).
Meta-analysis of 173 rate measurements from 21 publications was used to develop rate laws for chalcopyrite dissolution under environmentally relevant conditions. Multiple linear regression analysis of 28 data for nonoxidative chalcopyrite dissolution in the presence of O2 and Cl produced the following rate law: r = 10 - 1.52 e - 28200 / RT [ H + ] 1.68 Here, r is the rate of chalcopyrite dissolution in units of mol m−2  s−1 where the surface area is expressed on a geometric basis. Multiple linear regression analysis of 36 data for chalcopyrite dissolution caused by reaction with Fe(III) in the presence and absence of O2 and Cl produced the following rate law: r = 10 1.88 e - 48100 / RT [ H + ] 0.8 [ Fe ( III ) ] 0.42 Some data were excluded from these rate law models because they were inconsistent with the overall dataset and/or were relatively unconstrained. There were no published rate data that could be clearly identified as representing chalcopyrite dissolution caused by O2 oxidation alone. Although there are numerous reports that suggest that chalcopyrite dissolution rates are increased by the presence of Cl in solution, the regression models documented that the effect of Cl on dissolution was insignificant for this dataset. The rate laws developed in this work are most appropriate for characterizing chalcopyrite dissolution at low pH (⩽3), and will ultimately allow better modeling of acid, sulfate, Fe, and Cu release to the environment.

Samples of authigenic material, sediment overlying water and oxic surface sediment (0–0.5-cm depth) from a perennially oxygenated lacustrine basin were analysed to investigate which solid phases are important for binding a suite of trace elements (Ag, As, Ca, Cd, Cu, Hg, In, methylmercury (MeHg), Mg, Mo, Pb, Sb and Zn). The authigenic material, which was collected with inert Teflon sheets deployed for several years across the sediment–water interface, contained mainly poorly crystallized Fe oxyhydroxides and natural organic matter, presumably humic substances derived from the watershed. Manganese oxyhydroxides were not present in the collected authigenic material due to the slightly acidic condition (pH = 5.6) of the lake that prevents the formation and recycling of these compounds. Conditional equilibrium constants for the adsorption of cationic (K Fe–M) and anionic (K Fe–A) trace elements onto the authigenic Fe oxyhydroxides were estimated from their concentrations in the authigenic material and in bottom water samples. These field-derived values of K Fe–M and K Fe–A were compared with those predicted by the surface complexation model, using laboratory-derived intrinsic adsorption constants and the water composition at the study site. Equilibrium constants (K POM–M) were also calculated for the adsorption of the cationic trace elements onto the humic substances contained in the diagenetic material. The field-derived values of K POM–M were compared to those predicted by the speciation code WHAM 6 for the complexation of the trace elements by dissolved humic substances in the lake. Combining the results of the present study with those on the distributions of trace elements in the porewater and solid-phase sediments reported in previous studies at the same site, it was determined whether the trace elements bind preferentially to Fe oxyhydroxides or natural organic matter in oxic sediments. The main inferences are that the anionic trace elements As, Mo and Sb, as well as the cationic metal Pb are preferentially bound to the authigenic Fe oxyhydroxides whereas the other trace elements, and especially Hg and MeHg, are preferentially bound to the humic substances.

Isotopic and geochemical evidence of recharge sources and water quality in the Quaternary aquifer beneath Jinchang city, NW China by Jinzhu Ma; Feng Pan; Lihua Chen; W. Mike Edmunds; Zhenyu Ding; Jianhua He; Kunpeng Zhou; Tianming Huang (996-1007).
Multiple isotopic and hydrogeochemical tracers were utilized to understand the recharge sources and geochemical evolution of groundwater in the Quaternary aquifer beneath Jinchang city and the adjacent Gobi desert area. The groundwater shows markedly depleted stable isotopic composition compared to modern rainfall. The signature of groundwaters from Jinchang and the northern Gobi desert area differ clearly from that of the alluvial fan in the south Yongchang basin and modern rainfall, and has lower or non-detectable 3H activity, implying that the aquifer is likely maintained by palaeowater. This groundwater in the Gobi desert has a 14C age older than 12 ka, indicating that the groundwater resources are non-renewable. The build-up of dissolved solids through evaporation is a major control on groundwater composition, and the dominant anion species change systematically from HCO 3 - , SO 4 2 - to Cl, but cations from weathering of albite, calcite, dolomite and gypsum also make a significant contribution. The scientific results have important implications for groundwater management in Jinchang city and as well as in the Shiyang River basin under China’s West Development Strategy. It is recommended that the water allocation program of diverting water from the Dongda river to the Minqin basin be reconsidered.

Interaction of gypsum with lead in aqueous solutions by J.M. Astilleros; A. Godelitsas; J.D. Rodríguez-Blanco; L. Fernández-Díaz; M. Prieto; A. Lagoyannis; S. Harissopulos (1008-1016).
Sorption processes on mineral surfaces are a critical factor in controlling the distribution and accumulation of potentially harmful metals in the environment. This work investigates the effectiveness of gypsum (CaSO4⋅2H2O) to sequester Pb. The interaction of gypsum fragments with Pb-bearing solutions (10, 100 and 1000 mg/L) was monitored by performing macroscopic batch-type experiments conducted at room temperature. The aqueous phase composition was periodically determined by Atomic Absorption Spectrometry (AAS), Ion Chromatography (IC) and Inductively Coupled Plasma Optical Emission Spectroscopy (ICP–OES). Regardless of the [Pbaq]initial, a [Pbaq]final  < 4 mg/L was always reached. The uptake process was fast (t  < 1 h) for [Pbaq]initial  ⩾ 100 mg/L and significantly slower (t  > 1 week) for [Pbaq]initial  = 10 mg/L. Speciation calculations revealed that after a long time of interaction (1 month), all the solutions reached equilibrium with respect to both gypsum and anglesite. For [Pbaq]initial  ⩾ 100 mg/L, sorption takes place mainly via the rapid dissolution of gypsum and the simultaneous formation of anglesite both on the gypsum surface and in the bulk solution. In the case of [Pbaq]initial  = 10 mg/L, no anglesite precipitation was observed, but surface spectroscopy (proton Rutherford Backscattering Spectroscopy, p-RBS) confirmed the formation of Pb-bearing surface layers on the (0 1 0) gypsum surface in this case also. This study shows that the surface of gypsum can play an important role in the attenuation of Pb in contaminated waters.

Occurrence and geochemistry of arsenic in the groundwater of Eastern Croatia by M. Ujević; Ž. Duić; C. Casiot; L. Sipos; V. Santo; Ž. Dadić; J. Halamić (1017-1029).
In order to examine the extent of the As enrichment and the factors influencing this enrichment in the groundwater of Eastern Croatia, groundwater samples were collected from 56 production wells in two counties, Osijek-Baranja and Vukovar-Srijem, suspected to be more affected. Hydrochemical analyses were performed at all locations including in situ As speciation at 32 locations. Arsenic was detected in 46 out of 56 groundwater samples with total As concentrations up to 491 μg/L. Thirty-six of the studied wells yielded groundwater with total As concentrations that exceeded the WHO Maximum Contaminant Level for arsenic in drinking water of 10 μg/L. Only inorganic As species were detected with arsenite As(III) as the predominant form. The spatial distribution of As in the groundwater was significantly linked with geological, geomorphological and hydrogeological development of the alluvial basin of the Drava and Sava rivers. The most probable groundwater As sources are deeper sediments from the Middle and Upper Pleistocene. The results obtained suggest that biogeochemical processes controlling As concentration in the groundwater are complex and location-specific. Reductive dissolution of Fe oxides, desorption of As from Fe oxides and/or clay minerals as well as competition for the sorption sites with organic matter and phosphate could be the principal mechanisms that control As mobilization. The extent of those processes vary in the different parts of the Drava and Sava depressions and could be linked to different site related parameters, such as lithology, mineralogy, local hydrology and hydrogeology; thus different processes of As mobilization have been proposed for the different types of water in relation to groundwater evolution.

A test comparing concentrations of 57 chemical elements (Ag, Al, As, B, Ba, Be, Bi, Ca, Cd, Ce, Co, Cr, Cs, Cu, Dy, Er, Eu, Fe, Ga, Gd, Ge, Hf, Ho, I, K, La, Li, Lu, Mg, Mn, Mo, Na, Nb, Nd, Ni, Pb, Pr, Rb, Sb, Se, Sm, Sn, Sr, Ta, Tb, Te, Th, Ti, Tl, Tm, U, V, W, Y, Yb, Zn and Zr) determined by inductively coupled plasma quadrupole mass spectrometry (ICP-QMS) in 294 samples of the same bottled water (predominantly mineral water) sold in the European Union in glass and PET bottles demonstrates significant (Wilcoxon rank sum test, α  = 0.05) differences in median concentrations for Sb, Ce, Pb, Al, Zr, Ti, Th, La, Pr, Fe, Zn, Nd, Sn, Cr, Tb, Er, Gd, Bi, Sm, Y, Lu, Dy, Yb, Tm, Nb and Cu. Antimony has a 21× higher median value in bottled water when sold in PET bottles (0.33 vs. 0.016 μg/L). Glass contaminates the water with Ce (19× higher than in PET bottles), Pb (14×), Al (7×), Zr (7×), Ti, Th (5×), La (5×), Pr, Fe, Zn, Nd, Sn, Cr, Tb (2×), Er, Gd, Bi, Sm, Y, Lu, Yb, Tm, Nb and Cu (1.4×). Testing an additional 136 bottles of the same water sold in green and clear glass bottles demonstrates an important influence of colour, the water sold in green glass shows significantly higher concentrations in Cr (7.3×, 1.0 vs. 0.14 μg/L), Th (1.9×), La, Zr, Nd, Ce (1.6×), Pr, Nb, Ti, Fe (1.3×), Co (1.3×) and Er (1.1×).One hundred and twenty-six bottles of three different materials (glass, hard PET and soft PET) in 5 principal colours (clear, light and dark green and blue, brown) were subsequently washed and then filled with high purity water (18.2 MΩ cm). A portion of the bottles where left at the original average pH of the water (pH 6.5) while the remaining bottles were acidified to pH 3.5 with HNO3. Concentrations of the same 57 elements as above were determined after 1, 2, 3, 4, 5, 15, 30, 56, 80 and 150 days of leaching. Results substantiate the observations from the direct comparison of the same water sold in different bottle types (colour). For most elements leaching is enhanced at pH 3.5, and dark coloured bottles leach more than clear bottles, independent of bottle material. Values are still on the increase at the end of the test at 150 days. At that date the leachates showed a maximum concentration of 0.45 μg/L Sb, 0.3 μg/L Ce, 0.61 μg/L Pb, 68 μg/L Al and 0.06 μg/L Cr (all in glass at pH 3.5). None of the leachates approaches the maximum concentrations for drinking water as defined in European jurisdiction.

An occurrence of cadmiferous phosphorite soil concretions in Jamaica by Robert G. Garrett; Anthony R.D. Porter; Patricia A. Hunt (1047-1055).
Bauxite exploration drilling revealed the presence of phosphate minerals through the chemical and XRD analysis of recovered drill hole samples at Spitzbergen, in Manchester Parish, Jamaica. A subsequent pit led to the discovery of phosphorite concretions composed of hard competent masses of finely crystalline fluorapatite, with some minor crandallite. The phosphorite contains anomalously high levels of Zn (>5000 mg kg−1), Cd (>1.1%), Ag (>20 mg kg−1), Be (>80 mg kg−1) and, to a lesser extent, U. Textural and geochemical evidence indicates that the phosphorite concretions were most likely formed by the replacement of limestone by secondary deposition proximal to fossil guano deposits, postulated to be Late Miocene or Pliocene sea-bird colonies. Mechanical dispersion of the phosphorite concretions through karst weathering processes has led to their wider spatial distribution than the original guano deposits. Subsequent weathering of the concretions and the admixture of their decomposition products into the bauxitic and Terra Rossa soils is postulated to be the cause of the widespread anomalous levels of Zn, Cd and Be in these soils in central Jamaica, and the elevated levels of P in the bauxite.

Characterization of geosynthetic clay liner bentonite using micro-analytical methods by K. Lange; R.K. Rowe; H. Jamieson; R.L. Flemming; A. Lanzirotti (1056-1069).
In barrier design, familiarity of the structure and composition of the soil material at the micron scale is necessary for delineating the retention mechanisms of introduced metals, such as the formation of new mineral phases. In this study, the mineralogical and chemical makeup of the bentonite from a geosynthetic clay liner (GCL) was extensively characterized using a combination of conventional benchtop X-ray diffraction (XRD) and micro X-ray diffraction (μXRD) with synchrotron-generated micro X-ray fluorescence (μXRF) elemental mapping and μXRD (S-μXRD). These methods allow for the non-destructive, in situ investigation of a sample, with μm spatial resolution. Synchrotron-based hard X-ray microprobes are specifically advantageous to the study of trace metals due to higher spatial resolution (<10 μm) and higher analytical sensitivity (femtogram detection) than is possible using normal laboratory-based instruments. Minerals comprising less than 5% of the total bentonite sample such as gypsum, goethite and pyrite were identified that were not accessible by other conventional methods for the same GCL bentonite. Two dimensional General Area Diffraction Detector System (GADDS) images proved to be particularly advantageous in differentiating between the microcrystalline clay, which appeared as homogeneous Debye rings, and the ‘spotty’ or ‘grainy’ appearance of primary, more-coarsely-crystalline, accessory minerals. For S-μXRD, the tunability of the synchrotron X-rays allowed for efficient distinction of both clay minerals at low scattering angles and in identifying varying Fe oxide minerals at higher angles. GCL samples permeated with metal-bearing mining solutions were also examined in order to consider how mechanisms of metal attenuation may be identified using the same techniques. In addition to the cation exchange capacity from the montmorillonite clay, tests showed how minerals comprising only 1–2% of the bentonite such as goethite could potentially play a significant role in sequestering a range of metals, specifically Ni, Zn and Cu.

Pb isotope evidence for contaminant-metal dispersal in an international river system: The lower Danube catchment, Eastern Europe by Graham Bird; Paul A. Brewer; Mark G. Macklin; Mariyana Nikolova; Tsvetan Kotsev; Mihail Mollov; Catherine Swain (1070-1084).
Lead isotope signatures (207Pb/206Pb, 208Pb/206Pb, 208Pb/204Pb, 206Pb/204Pb), determined by magnetic sector ICP-MS in river channel sediment, metal ores and mine waste, have been used as geochemical tracers to quantify the delivery and dispersal of sediment-associated metals in the lower Danube River catchment. Due to a diverse geology and range of ore-body ages, Pb isotope signatures in ore-bodies within the lower Danube River catchment show considerable variation, even within individual metallogenic zones. It is also possible to discriminate between the Pb isotopic signatures in mine waste and river sediment within river systems draining individual ore bodies. Lead isotopic data, along with multi-element data; were used to establish the provenance of river sediments and quantify sedimentary contributions to mining-affected tributaries and to the Danube River. Data indicate that mining-affected tributaries in Serbia and Bulgaria contribute up to 30% of the river channel sediment load of the lower Danube River. Quantifying relative sediment contributions from mining-affected tributaries enables spatial patterns in sediment-associated metal and As concentrations to be interpreted in terms of key contaminant sources. Combining geochemical survey data with that regarding the provenance of contaminated sediments can therefore be used to identify foci for remediation and environmental management strategies.

Adsorption and desorption of phosphate on limestone in experiments simulating seawater intrusion by René M. Price; M. Reza Savabi; Jean L. Jolicoeur; Srikumar Roy (1085-1091).
This study investigates the potential release of PO 4 3 - from carbonate aquifers exposed to seawater intrusion. Adsorption and desorption of PO 4 3 - in the presence of deionized water (DIW) and seawater were conducted on a large block of Pleistocene age limestone to simulate the effects of seawater intrusion into a coastal carbonate aquifer at the laboratory scale. The limestone showed strong adsorption of PO 4 3 - in DIW, while adsorption was significantly less in the presence of seawater. Dissolution of CaCO3 was found to prevent PO 4 3 - adsorption at salinities less than 30 psu. Adsorption of PO 4 3 - was limited at higher salinities (30–33 psu), due to competition with HCO 3 - ions for adsorption sites. At a salinity <33, some PO 4 3 - absorption occurred as CaCO3 precipitated. Concentrations of PO 4 3 - between 2 and 5 μmol/L were released by desorption when the limestone was exposed to seawater. The results of this study suggest that as seawater intrudes into an originally freshwater coastal aquifer, adsorbed PO 4 3 - may be released into the groundwater. Consequently, adsorbed PO 4 3 - is expected to be released from coastal carbonate aquifers world-wide as sea level continues to rise exposing more of the freshwater aquifer to seawater.

Erratum to “Establishing constraints on groundwater ages with 36Cl, 14C, 3H, and noble gases: A case study in the eastern Paris basin, France” [Applied Geochemistry 25 (1) (2010) 123–142] by Véronique Lavastre; Corinne Le Gal La Salle; Jean-Luc Michelot; Sophie Giannesini; Lucilla Benedetti; Joël Lancelot; Bernard Lavielle; Marc Massault; Bertrand Thomas; Eric Gilabert; Didier Bourlès; Norbert Clauer; Pierre Agrinier (1092-1093).